Pressurized fluid systems are typically provided with valves that can operate (open/close) under overpressure conditions. In practice, a system including pressure sensor, logic solver and valve with actuator is often used. When the fluid pressure reaches the predetermined level, the sensor will detect the large increase in fluid pressure, and the logic solver will send command to the actuator to open/close the valve after getting the signal from the sensor.
The safety of the pressurized fluid systems protected by pressure sensor, logic solver and valve is threatened when the valve does not open/close as expected, such as when the sensor fails or the transmission of signal between sensor and the logic server fails or the transmission of command between logic server and valve interrupts.
Some other fail-safe valve systems that can also open/close automatically under overpressure condition use a collapsible pin arrangement, such as taught by U.S. Pat. No. 4,724,857 & U.S. Pat. No. 6,666,230 issued to Taylor and U.S. Pat. No. 6,651,686 issued to Scantlin and Cravens. In such systems, the pin is placed under compressive loading along an axial direction of the pin by the pressure of the fluid. A sufficient increase in fluid pressure above a nominal operational level causes the pin to buckle, or collapse, allowing a plunger or other mechanism to move to trigger the operation of the actuated valves.
A valve system can be advantageously configured to open or close in response to the collapse of a collapsible pin. However, system forces can undesirably affect a threshold pressure level at which the pressure responsive member begins to fail. For example, friction forces and fluidic pressure can tend to offset the compressive loading upon a collapsible pin if the pin actuation and the valve are directly coupled.
There is therefore a continued need for improvements in the art to increase the accuracy and repeatability of the protection systems, and it is to such improvements that the present invention is directed.
An actuated valve system is provided to operate (open/close) automatically under overpressure condition. The system includes a spring actuator assembly, an on/off valve assembly, a lock mechanism with one locking yoke and two rotatable locking handles, a collapsible pin type pressure sensing assembly and a pressure sensing line. The function of the pressure sensing line is to connect the upstream of the valve assembly with the body cavity of the collapsible pin type pressure sensing assembly, and in such a way the plunger undertakes the pressure upstream of the valve assembly.
Collapsible pin type pressure sensing assembly is the trigger unit of the whole system, and it mainly includes pin nut, pin cage, collapsible pin, body, and plunger assembly comprised by plunger, stem and locking yoke. The function of the collapsible pin type pressure sensing assembly is designed based on Euler's theory regarding the buckling of slim column subject to compressive force and realized by changing the plunger assembly's working positions.
The plunger of the collapsible pin type pressure sensing assembly bears the force due to the pressure in the upstream pipeline, and the force is transmitted to the collapsible pin by the second plunger stem. When the pressure in upstream pipeline is lower than the predetermined level, the axial force in the collapsible pin is below the threshold buckling value, and thus the collapsible pin is in a stable state, and the plunger assembly is in its first position. In this position, the locking yoke, which is rigidly connected with the first plunger stem, locks the rotatable locking handles, and the rotatable locking handles hold the motive element through the supporting rod of the spring actuator assembly, and the valve assembly is in the usual position.
When the pressure in the upstream pipeline is higher than the predetermined level, the axial force in the collapsible pin is over the threshold buckling value and simultaneously the collapsible pin buckles and loses its load-supporting capability. Due to the loss of the propulsive force from the collapsible pin, the plunger assembly, which is pushed by the pressure inside of the pipeline, moves to its second position. In this process, the locking yoke moves until losing its restriction on the rotatable locking handles, and then the rotatable locking handles releases the supporting rod of spring actuator assembly, and the spring actuator assembly drives the valve assembly to its unusual position, and thus the automatic operation (open/close) of the on/off valve assembly under overpressure condition is realized.
In this application, the collapsible pin type pressure sensing assembly realizes the function of pressure sensor and logic solver, and thus the whole system does not need any sensors and signal transmission, and the design is simple and reliable.